CN101362143A - A process and device for efficiently recycling waste printed circuit board solder - Google Patents

Abstract

A process and device for efficiently recycling waste printed circuit board solder. In a system where a sealed liquid heat-conducting medium exists, put the waste printed circuit soldered with electronic components into a rotating body with multiple filter holes. Immerse in the heat-conducting medium, raise the temperature until the solder melts, and when the temperature is constant, rotate the rotor to perform centrifugal solid-liquid separation, the solder leaks out from the filter hole and deposits at the bottom, and cools to form an ingot, and the electronic components are also separated from the waste printing accordingly circuit board. The invention provides a method for recycling waste printed circuit board solder with no environmental pollution, low energy consumption and high efficiency, and creates good conditions for efficient recycling of other metals.

Description

A process and device for efficiently recycling waste printed circuit board solder

technical field

The invention belongs to the technical field of resource recovery and reuse of waste electronic and electrical products, and relates to a new process for recycling waste printed circuit board solder.

Background technique

The present invention is a process for recycling solder in a large number of waste printed circuit boards (printed circuit board, PCB) research and development at present. As we all know, with the rapid development of the economy and the electronic information industry, the replacement of electronic and electrical products is increasing, and the service life of products is shortened, resulting in a large number of electronic products being discarded. Waste printed circuit boards are a major part of electronic waste, and their recycling has become a global problem that needs to be solved urgently. Waste printed circuit boards contain a large amount of solder, which has valuable recycling value. The recycling of solder has become an important issue in the recycling of waste printed circuit boards. At present, there have been some studies on the recovery of solder in waste printed circuit boards, but so far there is no reasonable method that can meet large-scale industrial recovery. Therefore, the recovery of solder is one of the difficult problems in today's waste printed circuit board recycling technology. one.

In China, the patent No. ZL200620070833.6 discloses a method that uses oil as a heating medium to heat the solder, and then removes the solder on the circuit board through ultrasonic vibration, thereby removing the components on the circuit board. The device used in this method is to process the circuit board piece by piece, and the solder will fall off through the action of ultrasonic waves. The purpose is to separate and recycle the electronic components on the waste printed circuit board to the maximum extent. There are certain limitations in the recycling of waste printed circuit boards. Patent No. 03157516.1 discloses a method and device for dismantling and recycling electronic components and solder of waste printed circuit boards. The recovery method is to heat all the solder joints of the circuit board to a molten state by hot air, then roll along the opposite direction of the circuit board movement through a mechanical roller brush close to the lower surface of the circuit board to be processed, and use the mechanical force of the bristles on the roller brush Sweeps the electronic components off the circuit board and is sucked up by the powerful suction head next to the roller brush to loosen and loose electronic components and solder alloy. This method uses continuous hot air to heat the circuit board and the action of a strong suction head will cause a lot of energy loss; the limitation of using a roller brush to remove solder is that the circuit board to be processed needs to face the side with solder to the roller brush, and the recovery efficiency is low. And some circuit boards have solder on both sides, it is difficult to completely recycle the solder.

Abroad, Canadian researcher McKesson Jr. et al. proposed that "by adding a strong base to increase the pH value of the solution to enhance the ability to dissolve tin and to add complexing agents for other metal ions to make these metal ions in a soluble state in the solution, and then use Electroplating method recovers tin and other metals from the above solution" process technology; British researcher Gibson. et al proposed "treating waste circuit boards with an acid solution containing Ti(IV) to dissolve tin or an alloy containing tin and lead into Sn(II) and Pb(II), then by the method of electrodeposition tin ion and lead ion are reduced to metallic tin and lead and reclaim.The above-mentioned method of reclaiming solder with hydrometallurgy not only energy consumption height, and the three waste treatment of generation Difficult and costly.

NEC Corporation of Japan has developed a device for automatically dismantling electronic components in waste printed circuit boards. This device includes two heating units and two component removal units. The first removal unit is equipped with an impact thruster and a PCB return. arm, the second removal unit is equipped with a shear propeller. The PCB board is first heated in the air at a temperature exceeding the melting point of the solder for 70 seconds, the main components are removed in the first removal unit by the impact force of the pusher and the mechanical arm, and the remaining parts are at the same temperature in the second heating unit Under heat for another 30 seconds, all remaining components and solder are removed by a shear pusher. This device mainly utilizes infrared heating and a two-stage removal method (respectively using vertical and horizontal impact forces) to detach the perforated element and the surface element without causing any damage. A combination of heat, impact force and surface ablation techniques are then used to desolder 96% of the solder on the circuit board, which is used as raw material for refining lead and tin. This technology uses air as the heating medium, and the heat utilization rate is relatively low. It is necessary to increase the temperature to make the circuit board heated evenly so that the solder will fall off completely, and heating the circuit board in the air will cause some toxic elements to volatilize, thereby causing environmental pollution. Need Carry out airtight handling and disposal of toxic substances.

The German FAPS company has been studying the automatic disassembly method of waste printed circuit boards. It adopts the principle opposite to the automatic assembly of circuit boards to disassemble. The device sorts out useful components according to their shape. The main purpose of this method is to automatically disassemble electronic components in waste printed circuit boards, so as to sort out valuable electronic components for recycling, but the research on the recovery of solder is not comprehensive.

Zebedin et al. of Vienna University of Technology proposed a semi-automatic disassembly unit. This unit consists of four computers and several programmable logic controllers (Programmable Logic Controller, PLC), including a vision system, a transmission system, a solder removal system and a robot system. The vision system classifies chips into three categories: valuable, environmentally harmful, and others through a high-quality image detection system. The first two chips are removed by a hybrid desoldering-robotic process. The solder removal system is used to remove surface mount components (Surface Mounted Devices, SMD), and other complex connections are removed by robotic systems. After disassembly, the robotic system can also collect the components and transfer them to a subsequent processing system. This disassembly system uses high-tech means to disassemble waste printed circuit boards, the purpose is to separate the electronic components from the substrate, so as to recover the valuable components; the solder removal system only processes part of the components, and does not fully consider the recycling of solder .

In addition, there is also a particle collision operation method that uses particles to hit the printed circuit board to separate the components from the circuit board by the collision of the particles to the components; it is also proposed to use an electric soldering iron to melt the solder on the waste printed circuit board first, and then Use a brush to remove the solder on the surface, etc. The limitations of these methods are that they are not suitable for large-scale recycling, and the efficiency is extremely low.

At present, the recycling technology of waste printed circuit board solder is in the feasibility study stage, and its development is restricted by many aspects such as technology and economy. Therefore, it is necessary to comprehensively consider factors such as environmental protection, energy saving, equipment and technology, and find an effective method suitable for large-scale recycling of waste printed circuit board solder.

Contents of the invention

The purpose of the present invention is to provide a method for recycling waste printed circuit board solder with no environmental pollution, low energy consumption and high efficiency, and to create good conditions for efficient recycling of other metals.

The object of the present invention is also to provide a simple and convenient device used in the above process.

The process of the present invention is that, in a system where a sealed liquid heat-conducting medium exists, put the waste printed circuit boards to be processed soldered with electronic components into a rotating body provided with a plurality of filter holes, immerse in the heat-conducting medium, and heat up Until the solder is melted, when the temperature is constant, the rotor is rotated to separate the solid and liquid by centrifugation, the solder leaks out from the filter hole and deposits at the bottom, and is cooled into an ingot; the electronic components are also separated from the waste printed circuit board accordingly.

A cooling device is installed on the upper part of the system where the sealed liquid heat transfer medium exists to condense and reflux the volatile matter of the heat transfer medium.

The said constant temperature is 220°C-300°C.

The rotation speed is controlled at 800rpm-1000rpm.

The rotation time is 5-20min, and the rotation method is intermittent rotation.

The heat conduction medium adopts one of diesel oil, kerosene, paraffin oil, and methyl silicone oil.

The device of the present invention includes a sealed container and a rotating shaft. A rotatable hollow rotating body is arranged in the container. Filter holes are arranged on the hollow rotating body. The hollow rotating body is connected with the rotating shaft protruding from the container. device.

The cooling device is a cooling water jacket, which is arranged on the top of the container, set on the rotating shaft, and has a water inlet pipe and a water outlet pipe.

The hollow rotating body is a hollow cylinder with uniform filter holes on its side and bottom.

Because at present, it is very difficult to recover solder from waste circuit boards no matter whether it adopts high-temperature smelting method or hydrometallurgical process, and the existence of solder will be detrimental to the recovery process of other metals. Therefore, there is no breakthrough in the existing research on solder recovery technology in discarded circuit boards. However, the present invention uses oil as a heating medium to melt the solder, and then separates the solder from the waste printed circuit board by solid-liquid centrifugation, and centrifugation is one of the most effective methods for separating liquid and solid by centrifugal force. According to this idea, we have designed a process and device for recycling waste printed circuit board solder with no environmental pollution, low energy consumption and high efficiency.

The treatment method of the present invention is to put the waste printed circuit boards soldered with electronic components into the hollow rotating body, then completely immerse the hollow rotating body in the liquid heat-conducting medium, heat up to the melting of the solder, and discard the printed circuit boards. The solder has become liquid at this time, and after the temperature is constant, the hollow rotor is rotated rapidly for several minutes, and the solder is separated from the waste printed circuit board substrate due to centrifugal action, and is quickly released from the filter hole; A vortex is generated in the container, and the separated solder gathers together with this vortex, deposits at the bottom of the container, and becomes an ingot after cooling; as the solder is removed, the electronic components are also separated from the waste printed circuit board. In this way, the separation and recovery of the waste printed circuit board solder is realized simply and efficiently.

The structural features of the device of the present invention are:

In order to prevent the volatilization of the heat transfer medium and the pollution to the environment during the separation process, a cooling water jacket and a sealing sleeve are set above the liquid surface of the medium. The existence of the cooling water jacket makes the volatile matter of the heat transfer medium condense when it rises to the cooling water jacket. Liquefaction and reflux, in addition to reducing the vapor pressure of the system to ensure the safe operation of the system; the sealing sleeve adopts the mechanical principle of dynamic sealing to isolate the system from the outside, and the rotating shaft works normally through the sealing sleeve. The present invention has designed a light swivel. The rotating body is a hollow cylinder, and uniform filter holes are designed on its side and bottom. The purpose is that when the motor drives the drum to rotate at a high speed, the molten solder in the drum will be released quickly through the filter holes by the action of centrifugal force, and the circuit The board substrate and electronics remain inside the swivel.

Compared with the prior art, the present invention has the following advantages:

1. The entire recycling process is carried out in a sealed system without secondary pollution.

2. The process is simple, the conditions are easy to control, and it is suitable for large-scale recycling of waste printed circuit boards.

3. High recycling efficiency. After putting the waste printed circuit boards into the drum, the temperature is controlled at a temperature between 220°C and 300°C, the rotation speed is controlled at 800rpm to 1000rpm, and the rotation time only needs to be about 10min. Intermittent rotation is adopted to waste printed circuit boards. The solder on it can come off completely.

4. In this recycling process, the circuit board is basically not cracked, no chemical reaction is involved in the whole process, and no harmful substances are produced.

5. The heat conduction medium is one of diesel oil, kerosene, paraffin oil, methyl silicone oil, etc. Due to the uniform heating, the solder of the waste printed circuit board is easy to remove in a short time; the removed solder will not adhere to the waste printed circuit board or electronic components because it is in the oil medium.

6. High energy utilization rate. Due to the way of heating the liquid, the heat conduction efficiency is high and the energy loss is relatively small.

7. Use a cylindrical drum with sieve holes to centrifuge waste printed circuit boards, which is easy to filter and has a short operating time.

Description of drawings

Figure 1 is a schematic diagram of equipment for recycling waste printed circuit board solder.

Icon number: 1. Motor 2. Seal sleeve 3. Cooling device 4. Rotary shaft

5. Heat conduction medium 6. Stainless steel sealed container 7 Hollow. Swivel 8- Filter hole

Fig. 2 is the detinning experiment of waste circuit board of embodiment 1

Fig. 3 is the detinning experiment of the waste circuit board of embodiment 2

Fig. 4 is the detinning experiment of the waste circuit board of embodiment 3

Fig. 5 is the detinning experiment of the waste circuit board of embodiment 4

Detailed ways

The concrete implementation process of the present invention is

1. Pack waste printed circuit boards with electronic components into the hollow rotor 7 with filter holes 8, so that the hollow rotor 7 is filled with waste printed circuit boards.

2. Connect the lower stainless steel airtight container 6 with the cooling water jacket 3 of the upper cooling device 3 with a flange, so that the connecting surface is sealed.

3. After installing the device, pass the cooling water to heat up to above the melting point of the solder, then start the motor 1, so that the motor 1 drives the hollow rotor 7 to rotate rapidly, and stop the experiment after a few minutes of rotation. The rotation method can be one-time rotation or intermittent rotation (that is, under the condition that the total rotation time is constant, the rotation is uniformly divided into stages).

4. After the system cools down, take out a block of solder at the bottom of the container, and take out the discarded printed circuit board substrate and the fallen off electronic components from the hollow swivel 7 .

From the experimental results of the following examples, it can be seen that when the temperature of the system rises above 220°C (preferably 220°C-300°C), the solder on the circuit board can be melted and separated by centrifugation.

Considering the removal of solder before cracking the circuit board substrate, energy utilization and other factors, we have done multi-factor experiments, and obtained the following optimal conditions from the experiments: under the condition of the rotation speed of about 800 ~ 1000rpm, the temperature is controlled at 240℃～260℃, the rotation time is 5-20min (most preferably 10min), and the rotation method is intermittent rotation (evenly rotated in 2-4 times), the solder on the waste printed circuit board can be basically completely removed. The inventor has also done several quantitative experiments, that is, a certain amount of solder is soldered on a new circuit board substrate with solder holes, and the experiment is carried out under the above conditions. The experimental results show that the solder recovery rate of the experiment is nearly 100%.

Example 1

Load the waste circuit board, the oil temperature is 235°C, rotate for 5 minutes, the result is shown in Figure 2:

Experimental results: Some electronic components fell off, but a large number of electronic components were attached to the circuit board; some tin fell off, but some tin remained in the soldering holes.

Example 2

After loading the sample, the oil temperature is 240°C, and the oil is rotated twice for 10 minutes. The result is shown in Figure 3:

Experimental results: Most of the electronic components fell off, but there were still electronic components attached to the circuit board; a large amount of tin fell off, but a small amount of tin remained in the solder holes.

Example 3

After loading the sample, the oil temperature is 240°C, rotate three times for a total of 15 minutes, and heat to 240°C before each rotation to stabilize, the results are shown in Figure 4:

Experimental results: Most of the electronic components fell off, but there were still very few electronic components attached to the circuit board; a large amount of tin fell off, but there was still a small amount of tin remaining in the soldering holes.

Example 4

After loading the sample, the oil temperature is controlled at 240°C, rotated four times for a total of 10 minutes, and heated to 240°C before each rotation to stabilize. The results are shown in Figure 5. Experimental results: all electronic components fell off; There is no solder residue in it.

Claims (9)

1. A process for efficiently recycling the solder of waste printed circuit boards, which is characterized in that, in a system where a sealed liquid heat-conducting medium exists, the waste printed circuits to be processed soldered with electronic components are placed into a plurality of filter holes Submerged in the heat-conducting medium, the temperature is raised until the solder melts. After the temperature is constant, the rotor is rotated for centrifuge solid-liquid separation. The solder leaks out from the filter holes and deposits at the bottom, and cools into an ingot, and the electronic components are also corresponding of detached printed circuit boards. 2. A process for efficiently recycling waste printed circuit board solder according to claim 1, characterized in that a cooling device is installed on the upper part of the system where the sealed liquid heat transfer medium exists to condense and reflow the volatile matter of the heat transfer medium . 3. A process for efficiently recycling waste printed circuit board solder according to claim 1 or 2, characterized in that said constant temperature is 220°C-300°C. 4. A process for efficiently recycling waste printed circuit board solder according to claim 3, characterized in that the rotation speed is controlled at 800rpm-1000rpm. 5. A process for efficiently recycling waste printed circuit board solder according to claim 4, characterized in that the rotation time is 5-20 minutes, and the rotation mode is intermittent rotation. 6. A process for efficiently recycling waste printed circuit board solder according to claim 4, characterized in that the heat conducting medium is one of diesel oil, kerosene, paraffin oil, and methyl silicone oil. 7. A device for efficiently recycling waste printed circuit board solder, characterized in that it includes a sealed container (6), a rotating shaft (4), and a rotatable hollow rotor (7) is provided in the container (6). Filter holes (8) are arranged on the body (7), the hollow rotating body (7) is connected with the rotating shaft (4) extending out of the container, and a cooling device (3) is arranged on the upper part of the container. 8. A device for efficiently recycling waste printed circuit board solder according to claim 7, characterized in that the cooling device (3) is a cooling water jacket, which is set on the top of the container and is set on the rotating shaft , and has a water inlet pipe and a water outlet pipe. 9. A device for efficiently recycling waste printed circuit board solder according to claim 7, characterized in that the hollow swivel (7) is a hollow cylinder, and uniform filter holes (8) are provided on its side and bottom .

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